Gene Expression Profiling of Retinal Pigment Epithelium Establish a Diverse Role of Glucocorticoids in the Eye

Background and Objective Glucocorticoids are essential steroid hormones that regulate various metabolic and homeostatic functions in almost all physiological systems. Synthetic glucocorticoids are among the most commonly prescribed drugs for the treatment of numerous pathological conditions including autoimmune, allergic and ocular diseases. Glucocorticoids are mainly used for their potent anti‐inflammatory and immunosuppressive activities mediated through the glucocorticoid receptor. Emerging evidence indicates that the physiological and therapeutic actions of glucocorticoids are tissue‐, cell‐, and sex‐specific, suggesting the actions of glucocorticoids are more complex than previously recognized. While synthetic glucocorticoids are widely used in the ophthalmology clinic for the treatment of ocular diseases, little is yet known about the mechanism of glucocorticoid signaling in different layers of the eye. Glucocorticoid receptors have been shown to be expressed in different cell types of the eye such as cornea, lens, and retina, suggesting an important role of glucocorticoid receptor signaling in the physiology of these ocular tissues. Methods and Results In this study, we investigated the presence of functional glucocorticoid receptors in retinal pigment epithelial (RPE) cells. We show that glucocorticoid receptors are highly expressed in human RPE cell line (ARPE19) as demonstrated by real‐time PCR and immunoblots. These glucocorticoid receptors are functional as they translocate to the nucleus and activate the expression of target genes in response to the synthetic glucocorticoid, dexamethasone. Microarray analysis of ARPE19 treated with dexamethasone for 6 hours resulted in significant changes in thousands of genes compared to vehicle control, suggesting an important role of glucocorticoids in RPE cells. Following this observation, we examined the effects of glucocorticoids on RPE/choroid layer of mice. We show the presence of glucocorticoid receptors in flatmounts of mouse choroidal tissue ex vivo by fluorescence confocal microscopy. To investigate the role of glucocorticoid receptor signaling on gene expression in RPE in vivo, circulating glucocorticoids were first depleted from mice by bilateral adrenalectomy. Then, we performed RNA sequencing following intravitreal injections of dexamethasone in the eyes of adrenalectomized mice. RNA sequencing revealed significant and dose‐dependent changes in RPE genes associated with calcium signaling, neuronal inflammation and cell survival. Additionally, significant differences in the number of genes as well as the pattern of regulation were observed between RPE/choroids from male versus female mice, suggesting a potential sexual dimorphic influence of glucocorticoids in RPE. Conclusion Together, our results indicate a significant role of glucocorticoids in RPE in dose and sex‐dependent fashion. This could eventually demand the use of lower glucocorticoid doses, and the subsequent adjustment of the dose in males versus female patients to further minimize the risk of adverse effects. Support or Funding Information This research was supported by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .